Fluorescence Quenching Studies of Curcumin by Hydrogen Peroxide in Acetonitrile Solution |
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Authors: | M O Iwunze |
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Institution: | (1) Mechanical Engineering Department, Michigan State University, East Lansing, MI 48824, USA;(2) Present address: Caterpillar Inc., Peoria, IL 61629, USA; |
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Abstract: | Steady state quenching studies of curcumin, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, fluorescence by hydrogen peroxide were conducted in acetonitrile solution. A quenching rate constant, kq, of 1.05 × 1010 M–1 · s–1 was obtained with a short fluorescence lifetime of 347 ps. The reaction rate constant, which is within the diffusion-limited regime, is activation-controlled. The rate constant of deactivation of the thermally excited curcumin was 1.2 orders of magnitude more nonradiative (2.67 × 109 s–1) than radiative (2.16 × 108 s–1). The reaction was exothermic with a G° of –1.97 eV and solvent reorganization energy of 1.37 eV. These values indicate that the electron transfer reaction is solvent-mediated with electron transfer rate constant, kET, of 2.16 × 1010 s–1. |
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